C Program to construct a DFA which accepts L = {aN | N ≥ 1}

Let us take a string S of size N, we have to design a Deterministic Finite Automata (DFA) for accepting the language L = {aN | N ≥ 1}.

The string accepting the language L is {a, aa, aaa, aaaaaaa…, }.

Now the user has to enter a string, if that string is present in the given language, then print “entered string is Accepted”. Otherwise, print “entered string is not Accepted”.

DFA transition diagram for the given language is −

Example

Following is the C program to construct DFA which accepts the language L = {aN | N ≥ 1} −

#include<stdio.h>
int main() {
   char S[30];
   int l,i;
   int count = 0;
   printf("To implement DFA of language {aN | N ≥ 1} 
 enter input string:");
   scanf("%s",S);
   l=strlen(S);
   for (i=0;i<l;i++) {
      if(S[i]!='a') {
         printf("entered string is NOT ACCEPTED");
         getch();
         exit(0);
      }
      if (S[i] == 'a')
         count++;
      else
         printf("invalid input");
   }
   if (count == l && count != 0) {
      printf("entered string is accepted");
   }
   return 0;
}

Output

You will get the following output −

Run 1:
To implement DFA of language {aN | N >= 1}
enter input string:aaaa
entered string is accepted
Run 2:
To implement DFA of language {aN | N >= 1}
enter input string:badsaa
entered string is NOT ACCEPTED